<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>I</mml:mi><mml:mi>n</mml:mi><mml:mi>S</mml:mi><mml:mi>i</mml:mi><mml:mi>t</mml:mi><mml:mi>u</mml:mi></mml:math>Reduction of Charge Noise in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>GaAs</mml:mi><mml:mo>/</mml:mo><mml:msub><mml:mi>Al</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:msub><mml:mi>Ga</mml:mi><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml

Buizert, C.; Koppens, Frank H. L.; Pioro‐Ladrière, Michel; Tranitz, Hans-Peter; Vink, I. T.; Tarucha, Seigo; Wegscheider, Werner; Vandersypen, L. M. K.

doi:10.1103/physrevlett.101.226603

Cited by 86 publications

(108 citation statements)

References 25 publications

Supporting

Mentioning

101

Contrasting

Order By: Relevance

“…This is, of course, a familiar conundrum in all proposals of quantum computation. The outlook is nevertheless quite promising, since random fluctuations in the electrostatic potential can be suppressed by bias cooling 15 or by adding a negatively biased insulated top gate 16 in order to suppress leakage of electrons from the gates into the two-dimensional electron gas. Furthermore, intentional changes in the electrostatic potential for the purposes of two-qubit operations can be enhanced by a floating interdot capacitive gate.…”

Section: Discussionmentioning

confidence: 99%

“…[10][11][12][13] This makes it difficult to find samples suitable for spin qubit realization. Furthermore, typically the impurities do introduce some switching noise, [14][15][16][17] so that even in samples in which the impurities are all far enough from the DQD that a two-electron singlettriplet qubit can be accessed, the interdot exchange energy is still subject to random fluctuation, leading to gate errors and decoherence. [18][19][20] This necessitates operating in a parameter regime such that the sensitivity of the exchange energy to the charge noise is minimized, a so-called "sweet spot".…”

mentioning

confidence: 99%

See 1 more Smart Citation

Screening of charged impurities with multielectron singlet-triplet spin qubits in quantum dots

et al. 2011

View full text Add to dashboard Cite

Charged impurities in semiconductor quantum dots comprise one of the main obstacles to achieving scalable fabrication and manipulation of singlet-triplet spin qubits. We theoretically show that using dots that contain several electrons each can help to overcome this problem through the screening of the rough and noisy impurity potential by the excess electrons. We demonstrate how the desired screening properties turn on as the number of electrons is increased, and we characterize the properties of a double quantum dot singlet-triplet qubit for small odd numbers of electrons per dot. We show that the sensitivity of the multi-electron qubit to charge noise may be an order of magnitude smaller than that of the two-electron qubit.One of the most promising paths to scalable quantum computation is to use laterally defined double quantum dots (DQDs) in semiconductor heterostructures. The qubit is formed by the spin states of the two-electron DQD with total spin projection zero along the z axis. 1,2 Such a qubit is insensitive to spatially uniform magnetic field fluctuations, and, most importantly, amenable to fast electrical manipulation. 2,3 Recent experiments have made tremendous advances along these lines, demonstrating single-qubit initialization, arbitrary manipulation, and single-shot readout, all within a fraction of the coherence time of the qubit. 3-7 Preliminary steps toward an entangling two-qubit gate have also been reported. 8 In principle, successful completion of that program leaves the (admittedly enormous) challenge of scaling up to large numbers of qubits as the last remaining hurdle in the fabrication of a practical quantum computer.However, a practical issue has emerged which threatens to be a crippling impediment to continued rapid progress. The semiconductor samples used to create quantum dots invariably contain a number of charge impurity centers, perhaps 10 10 cm −2 in GaAs systems. 9 Even if the charge on these centers can be frozen to avoid switching noise, their presence inhibits access to the oneelectron-per-dot regime since the lowest energy states of the dot may be fragmented due to the roughened potential landscape. [10][11][12][13] This makes it difficult to find samples suitable for spin qubit realization. Furthermore, typically the impurities do introduce some switching noise, [14][15][16][17] so that even in samples in which the impurities are all far enough from the DQD that a two-electron singlettriplet qubit can be accessed, the interdot exchange energy is still subject to random fluctuation, leading to gate errors and decoherence. [18][19][20] This necessitates operating in a parameter regime such that the sensitivity of the exchange energy to the charge noise is minimized, a so-called "sweet spot". 21 In general, the charge noise problem is even more pernicious when performing twoqubit operations directly mediated by the Coulomb interaction, and one must again seek a sweet spot. 22,23 However, in practice, this strategy may not be sufficient since one typically cannot optimize ov...

show abstract

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Screening of charged impurities with multielectron singlet-triplet spin qubits in quantum dots

et al. 2011

View full text Add to dashboard Cite

show abstract

“…[52][53][54][55] Consider the current through a QPC connected to two leads. The current is sensitively dependent on the gate voltage applied to the QPC.…”

Section: Discussionmentioning

confidence: 99%

Spin relaxation in a Si quantum dot due to spin-valley mixing

Huang

2014

Phys. Rev. B

103

View full text Add to dashboard Cite

We study the relaxation of an electron spin qubit in a Si quantum dot due to electrical noise. In particular, we clarify how the presence of conduction-band valleys influences spin relaxation. In single-valley semiconductor quantum dots, spin relaxation is through the mixing of spin and envelope orbital states via spin-orbit interaction. In Si, the relaxation could also be through the mixing of spin and valley states. We find that the additional spin relaxation channel, via spinvalley mixing and electrical noise, is indeed important for an electron spin in a Si quantum dot. By considering both spin-valley and intra-valley spin-orbit mixings and Johnson noise in a Si device, we find that the spin relaxation rate peaks at the hot spot, where the Zeeman splitting matches the valley splitting. Furthermore, because of a weaker field dependence, the spin relaxation rate due to Johnson noise could dominate over phonon noise at low magnetic fields, which fits well with recent experiments.

show abstract

“…Modulation-doped GaAs/AlGaAs heterostructures possess several desirable attributes including very high mobility of the underlying two-dimensional electron gas (2DEG) and the relative ease of nanostructure fabrication. However, the presence of ionized dopants inherent to modulationdoping can have adverse effects on the behavior of nanostructures and are a possible source of decoherence for spin-qubits [9,10]. Ionized dopants can act as active trapping sites for electrons injected from the metal surface gate through the Schottky barrier [11], giving rise to random switching of the charge state of the impurities.…”

mentioning

confidence: 99%

“…Ionized dopants can act as active trapping sites for electrons injected from the metal surface gate through the Schottky barrier [11], giving rise to random switching of the charge state of the impurities. These fluctuations cause instability through a time-dependent potential landscape [10][11][12][13]. Methods such as 'bias cooling' in which nanostructures are cooled while a positive bias applied to the gates aid in reducing fluctuations [11], but charge noise is still believed to a dominant mechanism limiting gate fidelities in spin qubits [9].…”

mentioning

confidence: 99%

Field-effect-induced two-dimensional electron gas utilizing modulation-doped ohmic contacts

Mondal

Gardner

Watson

et al. 2014

Solid State Communications

View full text Add to dashboard Cite

Modulation-doped AlGaAs/GaAs heterostructures are utilized extensively in the study of quantum transport in nanostructures, but charge fluctuations associated with remote ionized dopants often produce deleterious effects. Electric field-induced carrier systems offer an attractive alternative if certain challenges can be overcome. We demonstrate a field-effect transistor in which the active channel is locally devoid of modulation-doping, but silicon dopant atoms are retained in the ohmic contact region to facilitate reliable lowresistance contacts. A high quality two-dimensional electron gas is induced by a field-effect and is tunable over a wide range of density. Device design, fabrication, and low temperature (T= 0.3K) transport data are reported.Nanostructures such as quantum point contacts and quantum dots fabricated on modulation-doped AlGaAs/GaAs heterostructures are widely used to explore nanoscale electron transport and are utilized extensively in spin-based approaches to quantum computing [1][2][3][4][5][6][7][8]. Modulation-doped GaAs/AlGaAs heterostructures possess several desirable attributes including very high mobility of the underlying two-dimensional electron gas (2DEG) and the relative ease of nanostructure fabrication. However, the presence of ionized dopants inherent to modulationdoping can have adverse effects on the behavior of nanostructures and are a possible source of decoherence for spin-qubits [9,10]. Ionized dopants can act as active trapping sites for electrons injected from the metal surface gate through the Schottky barrier [11], giving rise to random switching of the charge state of the impurities. These fluctuations cause instability through a time-dependent potential landscape [10][11][12][13]. Methods such as 'bias cooling' in which nanostructures are cooled while a positive bias applied to the gates aid in reducing fluctuations [11], but charge noise is still believed to a dominant mechanism limiting gate fidelities in spin qubits [9].

show abstract

InSituReduction of Charge Noise inGaAs/AlxGa1−x

Cited by 86 publications

References 25 publications

Screening of charged impurities with multielectron singlet-triplet spin qubits in quantum dots

Screening of charged impurities with multielectron singlet-triplet spin qubits in quantum dots

Spin relaxation in a Si quantum dot due to spin-valley mixing

Field-effect-induced two-dimensional electron gas utilizing modulation-doped ohmic contacts

Contact Info

Product

Resources

About